Area facilities, such as landfills, mines, tailing ponds, farms and collections of point sources such as industrial plants, can be a source of fugitive emissions of airborne matter that can contribute to a change in the local, regional and global air quality. Several techniques and methodologies have been developed and used to measure the fugitive emission rates from such area facilities. Such methodologies, however, have been hindered by confidence in, and uncertainties pertaining to, the accuracy of the methodologies. There is, therefore, a need to calibrate the measurement of the fugitive emission rate of a gas or gases from a source of interest (subject gas), large area sources in particular (see, for example, Tregoures et. al (1999), Babilotte et. al (2010) and Babilotte (2011)).
Several studies (e.g., Tregoures et. al (1999), Babilotte et. al (2010) and Babilotte (2011)) have tested a number of different methods for measuring fugitive emission rates and compared the results of these methods to each other. These studies, however, were unable to determine the accuracy of the methods relative to the actual emission rate from the landfills being measured. Thoma et. al, (2010) describes a method for validating measuring fugitive emission rates but does not describe methods for calibrating a particular fugitive emission rate measurement.
Lamb et al. (1986) and Howard et al. (1992) describe a tracer method of measuring a fugitive emission rate that involves release of a reference gas that is of a different composition than the subject gas; measurement of concentrations of both the subject gas and the tracer gas; integrating separately for the subject gas and the reference gas the concentration data along the horizontal; and computing the ratio of the integrated concentrations with the reference gas as the denominator and the subject gas in the numerator, and then multiplying this ratio by the reference gas discharge rate to obtain a fugitive emission rate measurement of the subject gas. This method measures fugitive emission rates by horizontally integrated concentrations and provides a determination of the fugitive emission rate and not a calibration of the fugitive emission rate.
Scharff et. al. (2003) discuss the calibration of measured fugitive emission rates using an inverse modelling technique involving the release and measurement of a standard that is different from the gas emitted by the source of interest. Scharff et al. do not, however, indicate or suggest that there can be different levels of confidence in the calibration of a fugitive emission rate measurement. Releasing a reference gas into an emission plume and measuring it does not necessarily mean that there is high confidence in the calibration. For example, if a subject gas emission plume extends from a ground surface to a height that is much higher than the reference gas plume, the reference gas plume occupies only the lower heights, and the wind velocity versus height relationship is assumed rather than measured. With such a situation, the comparison of the measured fugitive emission rate to the reference gas is only in the lower portion of the subject gas plume and not the middle or upper portions of the subject gas emission plume. The calibration of the subject gas emission rate is, thus, effectively only for the lower portion of the plume and not the entire plume.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.